The aim of the study is to explore host factors in tobacco dependence by studying non-dependent smokers ("chippers"). Theories of tobacco dependence predict that chronic use of tobacco should lead to dependence. Preliminary data collected by the investigator characterizes a population of aberrant smokers who regularly smoke a small number of cigarettes without any apparent dependence. The pilot data establishes that chippers inhale and absorb nicotine, but differ from dependent smokers in many respects, including smoking motives, smoking history, and family history of smoking. A series of studies is proposed to examine smoking behavior and the behavioral pharmacology of tobacco in this population. The studies focus on the role of nicotine in chippers smoking, comparing them with a group of regular smokers. One study explores how nicotine pharamcodynamics, pharmcokinetics, and metabolism may differ in chippers (compared to regular smokers). A nicotine titration study examines whether chippers attempt to regulate blood nicotine levels, while a companion study examines chippers' nicotine preference under neutral, stressful, and relaxing conditions. The development of a tobacco withdrawal syndrome is also examined and a self-monitoring study investigates the stimulus antecedents of smoking in chippers and regular smokers. Finally, chippers are compared to regular smokers on a battery of self-report measures of smoking history and psychosocial factors. Chippers' smoking behavior challenges simple theories of tobacco dependence; a systematic investigation of their smoking behavior may provide insight into the nature and development of tobacco dependence in the majority of smokers.